Devices incorporating internal chemical reactants contained in pouches, particularly for the generation of exothermic or endothermic reactions, have been commercially available for some time. These devices all contain at least two reactants which need to be kept separate until the desired time of activation, at which point the barrier(s) separating the reactants must be broken to allow the reactants to mix.
One typical manufacturing design of these types of pouches incorporates a frangible seal separating the reactants inside the pouch. A frangible seal is a seal that tends to fracture, break, crumble and/or fall apart, as opposed to stretching, twisting and/or plastically deforming, when the seal is placed under stress. In such a pouch, the frangible seal that keeps the reactants separate consists of a partially heat-sealed line between two sealable layers of film forming separate side-by-side chambers or reservoirs for the reactants, with the dividing seal line being a weaker bond between the sealable layers than the surrounding film or the perimeter seals which form the outer closures or sealed edges. With external force applied in a compressive action on the pouch, the design is such that the partially sealed line between the chambers would fail, allowing the liquid or liquids to migrate between the chambers, thus mixing and reacting to generate the required results. In other words, the user would place the pouch on a flat surface and press firmly with the flat of their hands to build enough internal pressure to rupture the internal seal.
There are inherent problems with this design. For example, the amount of force needed to rupture the dividing seal can sometimes not be met by a smaller, weaker or inexperienced user. A certain technique is required and an understanding of where to push and the required forces helps the user to press material against the center dividing seal so that the force is directed against the area where it is designed to fail. Additionally, even though the dividing seal is ruptured, sometimes only a partial mixing of the reactants occurs. Typically, the internal materials are not visible to the user, and therefore when the user feels the pressure release due to a failure of the inner dividing seal, they fail to massage the contents thoroughly to provide complete mixing, leaving much of the original materials in their respective chambers.
Furthermore, the dividing seal, which has to be strong enough to keep the materials separated during storage and transportation, but weak enough for the user to cause to fail with compression force, refuses to burst with any sort of pressure short of a critical failure of the surrounding film. In other words, the perimeter seals or the film itself may burst before the inner seal releases, thereby creating leaks, a mess and a failed activation.
Finally, quite often in an attempt to make it easier for the user to activate, the manufacturer will create a weaker seal which will fail with less pressure from the user. Many times, these seals will fail prematurely due to outside forces encountered during shipping and storage or at lowered atmospheric pressures such as during air cargo transportation, causing a defective product, and in certain situations, a dangerous result, depending on the contents. During manufacturing, it is also difficult to control the partial seal parameters required and hold that consistency throughout a production run. The manufacturing process needs to be very tightly controlled to achieve a reliable result. Yet even when the product is manufactured to correct specifications, the final result is very much operator dependant.
Another method of construction known in the art is a simple pouch within a pouch design where one reactant is loose in the outer pouch and the other, typically a liquid, is contained in the inner pouch, which is also disposed within the outer pouch. Much the same as the previous example, the user must cause the inner pouch to burst and release its contents without damaging the outer pouch. Sometimes the user must press the article flat on a surface as the previous example, or an alternative method is to twist the entire package to put stress on the inner pouch to overcome its integrity and cause it to leak into the outer pouch. One again, it is difficult to predict the point of failure and the aperture size and shape. Since again, this process is invisible to the user, failure to rupture or inadequate mixing is a likely outcome. And once again, people with weaker or smaller hands or lack of experience may have trouble rupturing the inner pouch.
Yet another problem with known pouches for internal mixing of reactants is their lack of ability to vent any byproduct gasses created by the chemical reaction. If any such gasses are not permitted to escape from the reaction chamber to the outside environment, a ballooning effect and dangerous catastrophic failure of the outer package may occur. For this reason the types of reactants that may be used in these pouches is severely limited because manufacturers cannot use chemicals that release significant amounts of gas during reaction.
There is a need for an improved design and construction of a pouch for internal mixture of segregated reactants that comprises one or more secure and separate reactant storage compartments that are safely and easily unsealed by a user who lacks size, strength, experience, and technical knowledge. Furthermore, there is a need for a pouch for internal mixture of segregated reactants that incorporates a venting system to open the spectrum of available reactants to include those that cause significant out-gassing.